1
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Luan M, Hou Z, Zhang B, Ma L, Yuan S, Liu Y, Huang G. Inter-Domain Repulsion of Dumbbell-Shaped Calmodulin during Electrospray Ionization Revealed by Molecular Dynamics Simulations. Anal Chem 2023; 95:8798-8806. [PMID: 37309130 DOI: 10.1021/acs.analchem.2c05630] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 06/14/2023]
Abstract
The mechanisms whereby protein ions are released from nanodroplets at the liquid-gas interface have continued to be controversial since electrospray ionization (ESI) mass spectrometry was widely applied in biomolecular structure analysis in solution. Several viable pathways have been proposed and verified for single-domain proteins. However, the ESI mechanism of multi-domain proteins with more complicated and flexible structures remains unclear. Herein, dumbbell-shaped calmodulin was chosen as a multi-domain protein model to perform molecular dynamics simulations to investigate the structural evolution during the ESI process. For [Ca4CAM], the protein followed the classical charge residue model. As the inter-domain electrostatic repulsion increased, the droplet was found to split into two sub-droplets, while stronger-repulsive apo-calmodulin unfolded during the early evaporation stage. We designated this novel ESI mechanism as the domain repulsion model, which provides new mechanistic insights into further exploration of proteins containing more domains. Our results suggest that greater attention should be paid to the effect of domain-domain interactions on structure retention during liquid-gas interface transfer when mass spectrometry is used as the developing technique in gas phase structural biology.
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Affiliation(s)
- Moujun Luan
- Department of Cardiology, The First Affiliated Hospital of USTC, University of Science and Technology of China, Hefei 230001, China
- School of Chemistry and Materials Science, University of Science and Technology of China, Hefei 230026, China
| | - Zhuanghao Hou
- Department of Cardiology, The First Affiliated Hospital of USTC, University of Science and Technology of China, Hefei 230001, China
- School of Chemistry and Materials Science, University of Science and Technology of China, Hefei 230026, China
| | - Buchun Zhang
- Department of Cardiology, The First Affiliated Hospital of USTC, University of Science and Technology of China, Hefei 230001, China
| | - Likun Ma
- Department of Cardiology, The First Affiliated Hospital of USTC, University of Science and Technology of China, Hefei 230001, China
| | - Siming Yuan
- School of Chemistry and Materials Science, University of Science and Technology of China, Hefei 230026, China
- Department of Pharmacy, The First Affiliated Hospital of USTC, University of Science and Technology of China, Hefei 230001, China
| | - Yangzhong Liu
- School of Chemistry and Materials Science, University of Science and Technology of China, Hefei 230026, China
- Department of Pharmacy, The First Affiliated Hospital of USTC, University of Science and Technology of China, Hefei 230001, China
| | - Guangming Huang
- Department of Cardiology, The First Affiliated Hospital of USTC, University of Science and Technology of China, Hefei 230001, China
- School of Chemistry and Materials Science, University of Science and Technology of China, Hefei 230026, China
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2
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Largy E, König A, Ghosh A, Ghosh D, Benabou S, Rosu F, Gabelica V. Mass Spectrometry of Nucleic Acid Noncovalent Complexes. Chem Rev 2021; 122:7720-7839. [PMID: 34587741 DOI: 10.1021/acs.chemrev.1c00386] [Citation(s) in RCA: 43] [Impact Index Per Article: 14.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
Abstract
Nucleic acids have been among the first targets for antitumor drugs and antibiotics. With the unveiling of new biological roles in regulation of gene expression, specific DNA and RNA structures have become very attractive targets, especially when the corresponding proteins are undruggable. Biophysical assays to assess target structure as well as ligand binding stoichiometry, affinity, specificity, and binding modes are part of the drug development process. Mass spectrometry offers unique advantages as a biophysical method owing to its ability to distinguish each stoichiometry present in a mixture. In addition, advanced mass spectrometry approaches (reactive probing, fragmentation techniques, ion mobility spectrometry, ion spectroscopy) provide more detailed information on the complexes. Here, we review the fundamentals of mass spectrometry and all its particularities when studying noncovalent nucleic acid structures, and then review what has been learned thanks to mass spectrometry on nucleic acid structures, self-assemblies (e.g., duplexes or G-quadruplexes), and their complexes with ligands.
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Affiliation(s)
- Eric Largy
- Univ. Bordeaux, CNRS, INSERM, ARNA, UMR 5320, U1212, IECB, F-33600 Pessac, France
| | - Alexander König
- Univ. Bordeaux, CNRS, INSERM, ARNA, UMR 5320, U1212, IECB, F-33600 Pessac, France
| | - Anirban Ghosh
- Univ. Bordeaux, CNRS, INSERM, ARNA, UMR 5320, U1212, IECB, F-33600 Pessac, France
| | - Debasmita Ghosh
- Univ. Bordeaux, CNRS, INSERM, ARNA, UMR 5320, U1212, IECB, F-33600 Pessac, France
| | - Sanae Benabou
- Univ. Bordeaux, CNRS, INSERM, ARNA, UMR 5320, U1212, IECB, F-33600 Pessac, France
| | - Frédéric Rosu
- Univ. Bordeaux, CNRS, INSERM, IECB, UMS 3033, F-33600 Pessac, France
| | - Valérie Gabelica
- Univ. Bordeaux, CNRS, INSERM, ARNA, UMR 5320, U1212, IECB, F-33600 Pessac, France
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3
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Daems E, Dewaele D, Barylyuk K, De Wael K, Sobott F. Aptamer-ligand recognition studied by native ion mobility-mass spectrometry. Talanta 2020; 224:121917. [PMID: 33379118 DOI: 10.1016/j.talanta.2020.121917] [Citation(s) in RCA: 11] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/09/2020] [Revised: 11/19/2020] [Accepted: 11/21/2020] [Indexed: 12/31/2022]
Abstract
The range of applications for aptamers, small oligonucleotide-based receptors binding to their targets with high specificity and affinity, has been steadily expanding. Our understanding of the mechanisms governing aptamer-ligand recognition and binding is however lagging, stymieing the progress in the rational design of new aptamers and optimization of the known ones. Here we demonstrate the capabilities and limitations of native ion mobility-mass spectrometry for the analysis of their higher-order structure and non-covalent interactions. A set of related cocaine-binding aptamers, displaying a range of folding properties and ligand binding affinities, was used as a case study in both positive and negative electrospray ionization modes. Using carefully controlled experimental conditions, we probed their conformational behavior and interactions with the high-affinity ligand quinine as a surrogate for cocaine. The ratios of bound and unbound aptamers in the mass spectra were used to rank them according to their apparent quinine-binding affinity, qualitatively matching the published ranking order. The arrival time differences between the free aptamer and aptamer-quinine complexes were consistent with a small ligand-induced conformational change, and found to inversely correlate with the affinity of binding. This mass spectrometry-based approach provides a fast and convenient way to study the molecular basis of aptamer-ligand recognition.
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Affiliation(s)
- Elise Daems
- BAMS Research Group, University of Antwerp, Groenenborgerlaan 171, 2020, Antwerp, Belgium; AXES Research Group, University of Antwerp, Groenenborgerlaan 171, 2020, Antwerp, Belgium
| | - Debbie Dewaele
- BAMS Research Group, University of Antwerp, Groenenborgerlaan 171, 2020, Antwerp, Belgium
| | - Konstantin Barylyuk
- BAMS Research Group, University of Antwerp, Groenenborgerlaan 171, 2020, Antwerp, Belgium
| | - Karolien De Wael
- AXES Research Group, University of Antwerp, Groenenborgerlaan 171, 2020, Antwerp, Belgium
| | - Frank Sobott
- BAMS Research Group, University of Antwerp, Groenenborgerlaan 171, 2020, Antwerp, Belgium; Astbury Centre for Structural Molecular Biology, University of Leeds, Leeds, LS2 9JT, UK; School of Molecular and Cellular Biology, University of Leeds, Leeds, LS2 9JT, UK.
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4
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Yu Y, Liu H, Yu Z, Witkowska HE, Cheng Y. Stoichiometry of Nucleotide Binding to Proteasome AAA+ ATPase Hexamer Established by Native Mass Spectrometry. Mol Cell Proteomics 2020; 19:1997-2015. [PMID: 32883800 PMCID: PMC7710143 DOI: 10.1074/mcp.ra120.002067] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/30/2020] [Revised: 08/04/2020] [Indexed: 11/06/2022] Open
Abstract
AAA+ ATPases constitute a large family of proteins that are involved in a plethora of cellular processes including DNA disassembly, protein degradation and protein complex disassembly. They typically form a hexametric ring-shaped structure with six subunits in a (pseudo) 6-fold symmetry. In a subset of AAA+ ATPases that facilitate protein unfolding and degradation, six subunits cooperate to translocate protein substrates through a central pore in the ring. The number and type of nucleotides in an AAA+ ATPase hexamer is inherently linked to the mechanism that underlies cooperation among subunits and couples ATP hydrolysis with substrate translocation. We conducted a native MS study of a monodispersed form of PAN, an archaeal proteasome AAA+ ATPase, to determine the number of nucleotides bound to each hexamer of the WT protein. We utilized ADP and its analogs (TNP-ADP and mant-ADP), and a nonhydrolyzable ATP analog (AMP-PNP) to study nucleotide site occupancy within the PAN hexamer in ADP- and ATP-binding states, respectively. Throughout all experiments we used a Walker A mutant (PANK217A) that is impaired in nucleotide binding as an internal standard to mitigate the effects of residual solvation on mass measurement accuracy and to serve as a reference protein to control for nonspecific nucleotide binding. This approach led to the unambiguous finding that a WT PAN hexamer carried - from expression host - six tightly bound ADP molecules that could be exchanged for ADP and ATP analogs. Although the Walker A mutant did not bind ADP analogs, it did bind AMP-PNP, albeit at multiple stoichiometries. We observed variable levels of hexamer dissociation and an appearance of multimeric species with the over-charged molecular ion distributions across repeated experiments. We posit that these phenomena originated during ESI process at the final stages of ESI droplet evolution.
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Affiliation(s)
- Yadong Yu
- Department of Biochemistry and Biophysics, University of California San Francisco, San Francisco, California, USA
| | - Haichuan Liu
- Department of OBGYN & Reproductive Sci, Sandler-Moore MS Core Facility, University of California San Francisco, San Francisco, California, USA
| | - Zanlin Yu
- Department of Biochemistry and Biophysics, University of California San Francisco, San Francisco, California, USA
| | - H Ewa Witkowska
- Department of OBGYN & Reproductive Sci, Sandler-Moore MS Core Facility, University of California San Francisco, San Francisco, California, USA.
| | - Yifan Cheng
- Department of Biochemistry and Biophysics, University of California San Francisco, San Francisco, California, USA; Howard Hughes Medical Institute, University of California San Francisco, San Francisco, California, USA.
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5
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Oh MI, Consta S. General solvation motifs of a charged linear macroion in an aqueous droplet. Mol Phys 2019. [DOI: 10.1080/00268976.2019.1596326] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/27/2022]
Affiliation(s)
- Myong In Oh
- Department of Chemistry, The University of Western Ontario, London, Ontario, Canada
| | - Styliani Consta
- Department of Chemistry, The University of Western Ontario, London, Ontario, Canada
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6
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Beveridge R, Migas LG, Das RK, Pappu RV, Kriwacki RW, Barran PE. Ion Mobility Mass Spectrometry Uncovers the Impact of the Patterning of Oppositely Charged Residues on the Conformational Distributions of Intrinsically Disordered Proteins. J Am Chem Soc 2019; 141:4908-4918. [PMID: 30823702 PMCID: PMC6488185 DOI: 10.1021/jacs.8b13483] [Citation(s) in RCA: 45] [Impact Index Per Article: 9.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
![]()
The
global dimensions and amplitudes of conformational fluctuations
of intrinsically disordered proteins are governed, in part, by the
linear segregation versus clustering of oppositely charged residues
within the primary sequence. Ion mobility-mass spectrometry (IM-MS)
affords unique advantages for probing the conformational consequences
of the linear patterning of oppositely charged residues because it
measures and separates proteins electrosprayed from solution on the
basis of charge and shape. Here, we use IM-MS to measure the conformational
consequences of charge patterning on the C-terminal intrinsically
disordered region (p27 IDR) of the cell cycle inhibitory protein p27Kip1. We report the range of charge states and accompanying
collisional cross section distributions for wild-type p27 IDR and
two variants with identical amino acid compositions, κ14 and
κ56, distinguished by the extent of linear mixing versus segregation
of oppositely charged residues. Wild-type p27 IDR (κ31) and
κ14, where the oppositely charged residues are more evenly distributed,
exhibit a broad distribution of charge states. This is concordant
with high degrees of conformational heterogeneity in solution. By
contrast, κ56 with linear segregation of oppositely charged
residues leads to limited conformational heterogeneity and a narrow
distribution of charged states. Gas-phase molecular dynamics simulations
demonstrate that the interplay between chain solvation and intrachain
interactions (self-solvation) leads to conformational distributions
that are modulated by salt concentration, with the wild-type sequence
showing the most sensitivity to changes in salt concentration. These
results suggest that the charge patterning within the wild-type p27
IDR may be optimized to sample both highly solvated and self-solvated
conformational states.
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Affiliation(s)
- Rebecca Beveridge
- The Michael Barber Centre for Collaborative Mass Spectrometry, The School of Chemistry, Manchester Institute for Biotechnology , University of Manchester , Manchester M13 9PL , U.K
| | - Lukasz G Migas
- The Michael Barber Centre for Collaborative Mass Spectrometry, The School of Chemistry, Manchester Institute for Biotechnology , University of Manchester , Manchester M13 9PL , U.K
| | - Rahul K Das
- Department of Biomedical Engineering and Center for Biological Systems Engineering , Washington University in St. Louis , Campus Box 1097, One Brookings Drive , St. Louis , Missouri 63130 , United States
| | - Rohit V Pappu
- Department of Biomedical Engineering and Center for Biological Systems Engineering , Washington University in St. Louis , Campus Box 1097, One Brookings Drive , St. Louis , Missouri 63130 , United States
| | - Richard W Kriwacki
- Structural Biology, MS 311, Room D1024F , St. Jude Children's Research Hospital , 262 Danny Thomas Place , Memphis , Tennessee 38105-3678 , United States
| | - Perdita E Barran
- The Michael Barber Centre for Collaborative Mass Spectrometry, The School of Chemistry, Manchester Institute for Biotechnology , University of Manchester , Manchester M13 9PL , U.K
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7
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Consta S, In Oh M, Kwan V, Malevanets A. Strengths and Weaknesses of Molecular Simulations of Electrosprayed Droplets. JOURNAL OF THE AMERICAN SOCIETY FOR MASS SPECTROMETRY 2018; 29:2287-2296. [PMID: 30259408 DOI: 10.1007/s13361-018-2039-2] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/01/2018] [Revised: 07/05/2018] [Accepted: 07/13/2018] [Indexed: 06/08/2023]
Abstract
The origin and the magnitude of the charge in a macroion are critical questions in mass spectrometry analysis coupled to electrospray and other ionization techniques that transfer analytes from the bulk solution into the gaseous phase via droplets. In many circumstances, it is the later stages of the existence of a macroion in the containing solvent drop before the detection that determines the final charge state. Experimental characterization of small (with linear dimensions of several nanometers) and short-lived droplets is quite challenging. Molecular simulations in principle may provide insight exactly in this challenging for experiments regime. We discuss the strengths and weaknesses of the molecular modeling of electrosprayed droplets using molecular dynamics. We illustrate the limitations of the molecular modeling in the analysis of large macroions and specifically proteins away from their native states. Graphical Abstract ᅟ.
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Affiliation(s)
- Styliani Consta
- Department of Chemistry, The University of Western Ontario, London, Ontario, N6A 5B7, Canada.
| | - Myong In Oh
- Department of Chemistry, The University of Western Ontario, London, Ontario, N6A 5B7, Canada
| | - Victor Kwan
- Department of Chemistry, The University of Western Ontario, London, Ontario, N6A 5B7, Canada
| | - Anatoly Malevanets
- Department of Chemistry, The University of Western Ontario, London, Ontario, N6A 5B7, Canada
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8
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Malevanets A, Oh MI, Sharawy M, Consta S. Landau–Ginzburg theory for ‘star’-shaped droplets. Mol Phys 2018. [DOI: 10.1080/00268976.2018.1513174] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/28/2022]
Affiliation(s)
- Anatoly Malevanets
- Department of Electrical and Computer Engineering, The University of Western Ontario, London, Ontario, Canada
| | - Myong In Oh
- Department of Chemistry, The University of Western Ontario, London, Ontario, Canada
| | - Mahmoud Sharawy
- Department of Chemistry, The University of Western Ontario, London, Ontario, Canada
| | - Styliani Consta
- Department of Chemistry, The University of Western Ontario, London, Ontario, Canada
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9
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Gülbakan B, Barylyuk K, Schneider P, Pillong M, Schneider G, Zenobi R. Native Electrospray Ionization Mass Spectrometry Reveals Multiple Facets of Aptamer–Ligand Interactions: From Mechanism to Binding Constants. J Am Chem Soc 2018; 140:7486-7497. [DOI: 10.1021/jacs.7b13044] [Citation(s) in RCA: 37] [Impact Index Per Article: 6.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/17/2022]
Affiliation(s)
- Basri Gülbakan
- Department of Chemistry and Applied Bioscience, ETH Zürich, CH-8093 Zürich, Switzerland
- Hacettepe University Institute of Child Health, Ihsan Dogramaci Children’s Hospital, Sıhhiye Square, 06100 Ankara, Turkey
| | - Konstantin Barylyuk
- Department of Chemistry and Applied Bioscience, ETH Zürich, CH-8093 Zürich, Switzerland
| | - Petra Schneider
- Department of Chemistry and Applied Bioscience, ETH Zürich, CH-8093 Zürich, Switzerland
| | - Max Pillong
- Department of Chemistry and Applied Bioscience, ETH Zürich, CH-8093 Zürich, Switzerland
| | - Gisbert Schneider
- Department of Chemistry and Applied Bioscience, ETH Zürich, CH-8093 Zürich, Switzerland
| | - Renato Zenobi
- Department of Chemistry and Applied Bioscience, ETH Zürich, CH-8093 Zürich, Switzerland
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10
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Consta S, Oh MI, Sharawy M, Malevanets A. Macroion–Solvent Interactions in Charged Droplets. J Phys Chem A 2018; 122:5239-5250. [DOI: 10.1021/acs.jpca.8b01404] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/07/2023]
Affiliation(s)
- Styliani Consta
- Department of Chemistry, The University of Western Ontario, London, Ontario, Canada N6A 5B7
| | - Myong In Oh
- Department of Chemistry, The University of Western Ontario, London, Ontario, Canada N6A 5B7
| | - Mahmoud Sharawy
- Department of Chemistry, The University of Western Ontario, London, Ontario, Canada N6A 5B7
| | - Anatoly Malevanets
- Department of Electrical and Computer Engineering, The University of University of Western Ontario, London, Ontario, Canada N6A 5B9
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11
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Oh MI, Consta S. What factors determine the stability of a weak protein-protein interaction in a charged aqueous droplet? Phys Chem Chem Phys 2018; 19:31965-31981. [PMID: 29177351 DOI: 10.1039/c7cp05043g] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/15/2022]
Abstract
Maintaining the interface of a weak transient protein complex transferred from bulk solution to the gaseous state via evaporating droplets is a critical question in the detection of the complex association (dissociation) constant by using electrospray ionization mass spectrometry (ESI-MS). Here we explore the factors that may affect the stability of a protein-protein interaction (PPI) using atomistic molecular dynamics (MD) modelling of a complex of ubiquitin (Ub) and the ubiquitin-associated domain (UbA) (RCSB PDB code ) and a non-covalent complex of diubiquitin (RCSB PDB code ) in aqueous droplets. A general method is presented to determine the protonation states of the complexes we investigate in particular, and that of a protein in general, under various pH conditions that an evaporating droplet acquires due to its change in size. We find that the combination of high temperature and high charge states of the protein complexes may destabilize the interface by creating new interfaces instead of a direct rupture of the initial stable interface. We provide evidence that highly charged protein complexes are found in droplets that form conical extrusions of the solvent on the surface due to charge-induced instability. This distinct droplet morphology leads to a higher solvent evaporation rate that assists in transferring the complex in the gaseous state without dissociation. The conical solvent protrusions expose on the droplet surface certain amino acids that otherwise would be solvated in a droplet with the protein complex of low charge states. The new vapor-protein interface does not have a direct effect on the stability of the PPI. A common way in experiments to stabilize the protein complexes in droplets is to reduce the protonation state of the proteins. Here we find that weakly bound protein complexes even at high protonation states can be stabilized by the presence of a small number of counterions, without affecting the protonation state of the protein. Our findings may provide guiding principles in ESI-MS experiments to stabilize weak transient PPIs.
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Affiliation(s)
- Myong In Oh
- Department of Chemistry, The University of Western Ontario, London, Ontario N6A 5B7, Canada
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12
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In Oh M, Paliy M, Consta S. “Star” morphologies of charged nanodrops comprised of conformational isomers. J Chem Phys 2018; 148:024307. [DOI: 10.1063/1.5011989] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/23/2023] Open
Affiliation(s)
- Myong In Oh
- Department of Chemistry, The University of Western Ontario, London, Ontario N6A 5B7, Canada
| | - Maxim Paliy
- Department of Chemistry, The University of Western Ontario, London, Ontario N6A 5B7, Canada
| | - Styliani Consta
- Department of Chemistry, The University of Western Ontario, London, Ontario N6A 5B7, Canada
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13
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Oh MI, Malevanets A, Paliy M, Frenkel D, Consta S. When droplets become stars: charged dielectric droplets beyond the Rayleigh limit. SOFT MATTER 2017; 13:8781-8795. [PMID: 29139530 DOI: 10.1039/c7sm02017a] [Citation(s) in RCA: 16] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/12/2023]
Abstract
When a nano-drop comprising a single spherical central ion and dielectric solvent is charged above a well-defined threshold, it acquires a stable star morphology. In contrast, conducting droplets, will undergo fission. Here we report combined atomistic molecular dynamics and continuum modelling study of star formation of droplets that contain a highly charged ion. We assume that in the continuum model the dielectric response is linear. In this linear continuum model, which is an extension of Rayleigh model, the energy of the drop is comprised of terms analogous to those in Rayleigh model, which are surface energy and electrostatic energy of dielectric droplet charged by a central point charge. We present the stability analysis of the continuum model to determine the threshold of instability. Indeed we find that the model accounts well for the onset of the instabilities. Molecular dynamics show that the number of points of the star-shaped nano-drops depends only on the surface tension, dielectric constant and size of the droplet, and on the magnitude of the charge of the central ion, but not on its sign. Intuitively, it is expected that when a spherical dielectric drop becomes unstable it would transform into a non-spherical finite shape of the same volume as the initial spherical shape with the point charge located in the drop interior. To test whether the extended Rayleigh model can account for the observed droplet shapes, we performed numerical simulations of the linear continuum model. Contrary to the expectations, the simulations of the extended Rayleigh model does not reproduce the stable star shapes found in the atomistic simulations, not even when we account for the bending rigidity and spontaneous curvature of the surface. We argue that the assumption that the dielectric response is linear breaks down if the droplet surface approaches the central macro-ion, where the electric field strength is such that dielectric saturation sets in. We envisage that for certain solvents, these stars could be made permanent by cross-linking, opening the way to the production of a novel class of highly-non-convex colloids.
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Affiliation(s)
- Myong In Oh
- Department of Chemistry, University of Cambridge, Lensfield Road, Cambridge, CB2 1EW, UK.
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14
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Oh MI, Consta S. Charging and Release Mechanisms of Flexible Macromolecules in Droplets. JOURNAL OF THE AMERICAN SOCIETY FOR MASS SPECTROMETRY 2017; 28:2262-2279. [PMID: 28801879 DOI: 10.1007/s13361-017-1754-4] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/13/2016] [Revised: 05/28/2017] [Accepted: 05/29/2017] [Indexed: 06/07/2023]
Abstract
We study systematically the charging and release mechanisms of a flexible macromolecule, modeled by poly(ethylene glycol) (PEG), in a droplet by using molecular dynamics simulations. We compare how PEG is solvated and charged by sodium Na+ ions in a droplet of water (H2O), acetonitrile (MeCN), and their mixtures. Initially, we examine the location and the conformation of the macromolecule in a droplet bearing no net charge. It is revealed that the presence of charge carriers do not affect the location of PEG in aqueous and MeCN droplets compared with that in the neutral droplets, but the location of the macromolecule and the droplet size do affect the PEG conformation. PEG is charged on the surface of a sodiated aqueous droplet that is found close to the Rayleigh limit. Its charging is coupled to the extrusion mechanism, where PEG segments leave the droplet once they coordinate a Na+ ion or in a correlated motion with Na+ ions. In contrast, as PEG resides in the interior of a MeCN droplet, it is sodiated inside the droplet. The compact macro-ion transitions through partially unwound states to an extended conformation, a process occurring during the final stage of desolvation and in the presence of only a handful of MeCN molecules. For charged H2O/MeCN droplets, the sodiation of PEG is determined by the H2O component, reflecting its slower evaporation and preference over MeCN for solvating Na+ ions. We use the simulation data to construct an analytical model that suggests that the droplet surface electric field may play a role in the macro-ion-droplet interactions that lead to the extrusion of the macro-ion. This study provides the first evidence of the effect of the surface electric field by using atomistic simulations. Graphical Abstract ᅟ.
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Affiliation(s)
- Myong In Oh
- Department of Chemistry, The University of Western Ontario, London, ON, N6A 5B7, Canada
| | - Styliani Consta
- Department of Chemistry, The University of Western Ontario, London, ON, N6A 5B7, Canada.
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15
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Liigand P, Heering Suu A, Kaupmees K, Leito I, Girod M, Antoine R, Kruve A. The Evolution of Electrospray Generated Droplets is Not Affected by Ionization Mode. JOURNAL OF THE AMERICAN SOCIETY FOR MASS SPECTROMETRY 2017; 28:2124-2131. [PMID: 28744770 DOI: 10.1007/s13361-017-1737-5] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/06/2017] [Revised: 05/22/2017] [Accepted: 06/11/2017] [Indexed: 06/07/2023]
Abstract
Ionization efficiency and mechanism in ESI is strongly affected by the properties of mobile phase. The use of mobile-phase properties to accurately describe droplets in ESI source is convenient but may be inadequate as the composition of the droplets is changing in the plume due to electrochemical reactions occurring in the needle tip as well as continuous drying and fission of droplets. Presently, there is paucity of research on the effect of the polarity of the ESI mode on mobile phase composition in the droplets. In this paper, the change in the organic solvent content, pH, and droplet size are studied in the ESI plume in both ESI+ and ESI- ionization mode. We introduce a rigorous way - the absolute pH (pHabsH2O) - to describe pH change in the plume that takes into account organic solvent content in the mobile phase. pHabsH2O enables comparing acidities of ESI droplets with different organic solvent contents. The results are surprisingly similar for both ionization modes, indicating that the dynamics of the change of mobile-phase properties is independent from the ESI mode used. This allows us to conclude that the evolution of ESI droplets first of all proceeds via the evaporation of the organic modifier and to a lesser extent via fission of smaller droplets from parent droplets. Secondly, our study shows that qualitative findings related to the ESI process obtained on the ESI+ mode can almost directly be applied also in the ESI- mode. Graphical Abstract ᅟ.
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Affiliation(s)
- Piia Liigand
- Institute of Chemistry, University of Tartu, Ravila 14a, 50411, Tartu, Estonia.
| | - Agnes Heering Suu
- Institute of Chemistry, University of Tartu, Ravila 14a, 50411, Tartu, Estonia
| | - Karl Kaupmees
- Institute of Chemistry, University of Tartu, Ravila 14a, 50411, Tartu, Estonia
| | - Ivo Leito
- Institute of Chemistry, University of Tartu, Ravila 14a, 50411, Tartu, Estonia
| | - Marion Girod
- CNRS, Université Claude Bernard Lyon 1, Ens de Lyon, Institut des Sciences Analytiques, University of Lyon, UMR 5280, 5 rue de la Doua, F-69100, Villeurbanne, France
| | - Rodolphe Antoine
- Université Claude Bernard Lyon 1, CNRS, Institut Lumière Matière, University of Lyon, UMR 5306, F-69622, Lyon, France
| | - Anneli Kruve
- Institute of Chemistry, University of Tartu, Ravila 14a, 50411, Tartu, Estonia
- Schulich Faculty of Chemistry, Technion-Israel Institute of Technology, Technion City, Haifa, 3200008, Israel
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Consta S, Sharawy M, Oh MI, Malevanets A. Advances in Modeling the Stability of Noncovalent Complexes in Charged Droplets with Applications in Electrospray Ionization-MS Experiments. Anal Chem 2017; 89:8192-8202. [DOI: 10.1021/acs.analchem.7b01941] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/20/2022]
Affiliation(s)
- Styliani Consta
- Department
of Chemistry, The University of Western Ontario, London, Ontario N6A 5B7, Canada
- Department
of Chemistry, University of Cambridge, Lensfield Road, Cambridge, CB2 1EW, United Kingdom
| | - Mahmoud Sharawy
- Department
of Chemistry, The University of Western Ontario, London, Ontario N6A 5B7, Canada
| | - Myong In Oh
- Department
of Chemistry, The University of Western Ontario, London, Ontario N6A 5B7, Canada
| | - Anatoly Malevanets
- Department
of Electrical and Computer Engineering, The University of Western Ontario, London, Ontario N6A 5B9, Canada
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17
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Porrini M, Rosu F, Rabin C, Darré L, Gómez H, Orozco M, Gabelica V. Compaction of Duplex Nucleic Acids upon Native Electrospray Mass Spectrometry. ACS CENTRAL SCIENCE 2017; 3:454-461. [PMID: 28573208 PMCID: PMC5445532 DOI: 10.1021/acscentsci.7b00084] [Citation(s) in RCA: 76] [Impact Index Per Article: 10.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/22/2017] [Indexed: 05/25/2023]
Abstract
We report on the fate of nucleic acids conformation in the gas phase as sampled using native mass spectrometry coupled to ion mobility spectrometry. On the basis of several successful reports for proteins and their complexes, the technique has become popular in structural biology, and the conformation survival becomes more and more taken for granted. Surprisingly, we found that DNA and RNA duplexes, at the electrospray charge states naturally obtained from native solution conditions (≥100 mM aqueous NH4OAc), are significantly more compact in the gas phase compared to the canonical solution structures. The compaction is observed for all duplex sizes (gas-phase structures are more compact than canonical B-helices by ∼20% for 12-bp, and by up to ∼30% for 36-bp duplexes), and for DNA and RNA alike. Molecular modeling (density functional calculations on small helices, semiempirical calculations on up to 12-bp, and molecular dynamics on up to 36-bp duplexes) demonstrates that the compaction is due to phosphate group self-solvation prevailing over Coulomb repulsion. Molecular dynamics simulations starting from solution structures do not reproduce the experimental compaction. To be experimentally relevant, molecular dynamics sampling should reflect the progressive structural rearrangements occurring during desolvation. For nucleic acid duplexes, the compaction observed for low charge states results from novel phosphate-phosphate hydrogen bonds formed across both grooves at the very late stages of electrospray.
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Affiliation(s)
- Massimiliano Porrini
- INSERM,
CNRS, Université de Bordeaux, Acides
Nucléiques Régulations Naturelle et Artificielle (ARNA,
U1212, UMR5320), IECB, 2 rue Robert Escarpit, 33607 Pessac, France
| | - Frédéric Rosu
- CNRS,
INSERM, Université de Bordeaux, Institut
Européen de Chimie et Biologie (IECB, UMS3033, US001), 2 rue Robert Escarpit, 33607 Pessac, France
| | - Clémence Rabin
- INSERM,
CNRS, Université de Bordeaux, Acides
Nucléiques Régulations Naturelle et Artificielle (ARNA,
U1212, UMR5320), IECB, 2 rue Robert Escarpit, 33607 Pessac, France
| | - Leonardo Darré
- The
Barcelona Institute of Science and Technology, Institute for Research in Biomedicine (IRB) Barcelona, Baldiri Reixac 10, 08028 Barcelona, Spain
- Joint
BSC-CRG-IRB Research Program in Computational Biology, IRB Barcelona, Barcelona, Spain
| | - Hansel Gómez
- The
Barcelona Institute of Science and Technology, Institute for Research in Biomedicine (IRB) Barcelona, Baldiri Reixac 10, 08028 Barcelona, Spain
- Joint
BSC-CRG-IRB Research Program in Computational Biology, IRB Barcelona, Barcelona, Spain
| | - Modesto Orozco
- The
Barcelona Institute of Science and Technology, Institute for Research in Biomedicine (IRB) Barcelona, Baldiri Reixac 10, 08028 Barcelona, Spain
- Joint
BSC-CRG-IRB Research Program in Computational Biology, IRB Barcelona, Barcelona, Spain
- Department
of Biochemistry and Biomedicine, University
of Barcelona, Avda Diagonal
647, 08028 Barcelona, Spain
| | - Valérie Gabelica
- INSERM,
CNRS, Université de Bordeaux, Acides
Nucléiques Régulations Naturelle et Artificielle (ARNA,
U1212, UMR5320), IECB, 2 rue Robert Escarpit, 33607 Pessac, France
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Kim D, Wagner N, Wooding K, Clemmer DE, Russell DH. Ions from Solution to the Gas Phase: A Molecular Dynamics Simulation of the Structural Evolution of Substance P during Desolvation of Charged Nanodroplets Generated by Electrospray Ionization. J Am Chem Soc 2017; 139:2981-2988. [DOI: 10.1021/jacs.6b10731] [Citation(s) in RCA: 41] [Impact Index Per Article: 5.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/09/2023]
Affiliation(s)
- Doyong Kim
- Department of Chemistry, Texas A&M University, College Station, Texas 77843, United States
| | - Nicole Wagner
- Department of Chemistry, Texas A&M University, College Station, Texas 77843, United States
| | - Kerry Wooding
- Department of Chemistry, Texas A&M University, College Station, Texas 77843, United States
| | - David E. Clemmer
- Department
of Chemistry, Indiana University, Bloomington, Indiana 47405, United States
| | - David H. Russell
- Department of Chemistry, Texas A&M University, College Station, Texas 77843, United States
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Oh MI, Consta S. Stability of a Transient Protein Complex in a Charged Aqueous Droplet with Variable pH. J Phys Chem Lett 2017; 8:80-85. [PMID: 27936321 DOI: 10.1021/acs.jpclett.6b02319] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 06/06/2023]
Abstract
Electrospray ionization mass spectrometry (ESI-MS) has the potential to become a high-throughput robust experimental method for the detection of protein-protein equilibrium constants. Poorly understood processes that affect the stability of weak noncovalent protein complexes in the intervening droplet environment are a significant factor that precludes the advancement of the method. We use molecular dynamics to study the stability of a ubiquitin and ubiquitin-associated domain complex (RCSB PDB code 2MRO ) in an aqueous droplet with changing size and charge concentration. We present evidence that a weak protein complex changes conformation and may dissociate in shrinking droplets. Then, the droplets containing these dissociated proteins divide. Our findings suggest that in some cases ESI-MS does not measure the correct association constants. The study intends to stimulate research for systematic development of experimental protocols that stabilize weakly bound protein interfaces in droplets.
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Affiliation(s)
- Myong In Oh
- Department of Chemistry, The University of Western Ontario , London, Ontario N6A 5B7, Canada
| | - Styliani Consta
- Department of Chemistry, The University of Western Ontario , London, Ontario N6A 5B7, Canada
- Department of Chemistry, University of Cambridge , Lensfield Road, Cambridge CB2 1EW, United Kingdom
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20
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Sharawy M, Consta S. Characterization of "Star" Droplet Morphologies Induced by Charged Macromolecules. J Phys Chem A 2016; 120:8871-8880. [PMID: 27797502 DOI: 10.1021/acs.jpca.6b08486] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/11/2023]
Abstract
"Star" morphologies of charged liquid droplets are distinct droplet conformations that, for a certain charge squared to volume ratio, have lower energy than their spherically shaped analogues. For these shapes to appear, the charge should be carried by a single ionic species. A typical example of a charge carrier that we employ in this study is a fully charged double-stranded oligodeoxynucleotide (dsDNA) in an aqueous and an acetonitrile droplet. We characterize the structure and dynamics of the star-shaped droplets. We find that by increasing the charge squared to volume ratio, the droplet evolves from spherical to "spiky" shapes, by first passing from droplet sizes that undergo enhanced shape fluctuations relative to those of the larger spherical droplets. These fluctuations mark the onset of the instability. We also find that in the spiky droplet, the orientation of the solvent molecules in the first shell about the dsDNA is very close to that in the bulk solution. However, this orientation is substantially different farther away from the dsDNA. With regards to dynamics, the motion of the spikes is reflected in the autocorrelation functions of rotationally invariant order parameters that show a damped oscillator form of decay, indicative of the elastic motion of the spikes. We compare the formation of spikes with that of the ferrofluids and the dielectric materials in an electric field, and we conclude that they represent a different entity that deserves its own characterization. The study provides insight into the manner in which the charge distribution may give rise to well-controlled droplet morphologies and calls for experiments in this direction.
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Affiliation(s)
- Mahmoud Sharawy
- Department of Chemistry, The University of Western Ontario , London, Ontario Canada N6A 5B7
| | - Styliani Consta
- Department of Chemistry, The University of Western Ontario , London, Ontario Canada N6A 5B7.,Department of Chemistry, University of Cambridge , Lensfield Road, Cambridge, CB2 1EW, United Kingdom
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